It is reported in The Japanese Journal of Nutrition, Vol. 20, No. 4, Pages 139-141, July, 1962 and Robert J. Nicolosi, The Summary presented at Georgia Rice Council in Jan. 13-16, 1991 that the intake of rice bran oil (as defined in JAS (Japan Agricultural Standards) 554, notified in the Ministry of Agricultural and Forestry) causes a remarkable decrease in harmful cholesterol level while not reducing but, on the contrary, increasing the so-called benign cholesterol in vivo. It is considered that rice bran oil contains a large amount of unsaponifiable matters which would exert useful physiological effects on human body.
In general, crude rice bran oil has a high acid value and can be refined to an edible level only at an extremely low yield of about 70%, compared with common edible vegetable oils which can be refined at a yield of 90% or above. Crude rice bran oil contains 5 to 6% of unsaponifiable matters which seemingly exert physiologically useful effects. However, the amount of these unsaponifiable matters present in edible rice bran oil, which has been refined by alkali refining, dewaxing, decoloring, deodorizing and/or finally filtering, is reduced to 2.5 to 3.5%. Namely, most of these unsaponifiable matters are not utilized but are disposed of. Further, crude rice bran oil contains about 2% of ferulates which may be similarly useful from a physiological viewpoint. However, the amount of ferulates in edible rice bran oil is reduced to about 0.1%. Namely, most of these ferulates are merely used as a starting material for producing oils for industrial use in the form of ferulic acid salts or a soapstock obtained as a by-product or in combination with other appropriate fatty acids.
Hitherto, the residue obtained in the refining process of rice bran oil is disposed but not effectively utilized, and therefore, a physiologically active substance (e.g., a phenolic substance) present therein tended to be removed together with useless materials. In general, a process which comprises recovering and concentrating the physiologically active substance from the residue in a suitable state, and adding the obtained product to a common edible rice bran oil refined has not been carried out because it is considered that impurity will become put back into the refined product.